Question Bizarre unable to power on issue, multiple identical PC's. Sorry, long post!

[Solan Goose]

3 years ago, I purchased 12 pc's from a prebuilt provider in the UK for work. All identical spec, all have worked flawlessly for 3 years until recently. I have had issues with 3 of these PC's which are all in the same office. It started off with one of the PC's initially and now all 3 have the exact same issue.

The symptoms were that they simply would not power on from the front panel power switch when shutdown overnight and turned on in the morning. This was an intermittent issue at first, only affecting one pc initially.

After unplugging from the mains and trying again several times, they would just suddenly come to life and power up. It got progressively worse with the first PC and I was convinced it was the power switch.

I replaced it and all was fine for a couple of days and it happened again. I was then thinking it was a PSU issue, so I replaced it with a tested fully working new one (same model) and it would still not power up. I then decided to short the power switch on the motherboard (should have done this first) and this did nothing. There was power to the mainboard as the lights on the mainboard were on and pulsating, but no fan movement at all from PSU, CPU or MB.

I was then thinking it must be another component or connection/cable issue. I literally took every component from the mainboard out, ram, gpu, ssd, all front panel connectors etc, so that it was basically a motherboard, cpu and PSU. Still NOTHING when shorting the power pins and using a switch. I also took out the CMOS battery for good measure.

At this point I was convinced that it must be the mainboard or cpu. I was at the point of taking the mainboard out of the chassis to see if there was some kind of chassis short. I left it overnight and decided to try again the next morning with a clean head as I was frustrated. It was on the workbench exactly where I left it. I shorted the pins and it powered on! I was amazed. I carefully connected all the components one at a time and it was fully working again, even the power switch. I tried shutting down, restarting multiple times and left it off for several hours and it fired up no problem every time. I was not sure what happened, but was just glad it was working again.

The most bizarre thing happened a few days later when the 2 other PC’s in the same office (exact same spec) were doing EXACTLY the same thing. I did the same thing, stripped them down and they would not power up at all even when shorting out the pins. I left them overnight again last night and guess what? Today they both powered on, no problem.

Please can someone explain this as I have NEVER come across anything like this before. We have 9 more of these PC's in other departments and they are working just fine. I thought there could be a power spike issue in the office, but I was working on these pc's in my own office in another building. Here are the specs:

CPU - AMD Ryzen 5 3600X
Motherboard - ASUS PRIME B450-PLUS
Memory - 8GB Corsair VENGEANCE DDR4 2666MHz (2 x 4GB)
Graphics Card - 1GB NVIDIA GEFORCE 710 - DVI, HDMI, VGA
SSD - 250GB Samsung 860 EVO 2.5"
Power Supply - CORSAIR VS-350

 

[Bob.B]

3 years ago, I purchased 12 pc's from a prebuilt provider in the UK for work. All identical spec, all have worked flawlessly for 3 years until recently. I have had issues with 3 of these PC's which are all in the same office. It started off with one of the PC's initially and now all 3 have the exact same issue.

The symptoms were that they simply would not power on from the front panel power switch when shutdown overnight and turned on in the morning. This was an intermittent issue at first, only affecting one pc initially.

After unplugging from the mains and trying again several times, they would just suddenly come to life and power up. It got progressively worse with the first PC and I was convinced it was the power switch.

I replaced it and all was fine for a couple of days and it happened again. I was then thinking it was a PSU issue, so I replaced it with a tested fully working new one (same model) and it would still not power up. I then decided to short the power switch on the motherboard (should have done this first) and this did nothing. There was power to the mainboard as the lights on the mainboard were on and pulsating, but no fan movement at all from PSU, CPU or MB.

I was then thinking it must be another component or connection/cable issue. I literally took every component from the mainboard out, ram, gpu, ssd, all front panel connectors etc, so that it was basically a motherboard, cpu and PSU. Still NOTHING when shorting the power pins and using a switch. I also took out the CMOS battery for good measure.

At this point I was convinced that it must be the mainboard or cpu. I was at the point of taking the mainboard out of the chassis to see if there was some kind of chassis short. I left it overnight and decided to try again the next morning with a clean head as I was frustrated. It was on the workbench exactly where I left it. I shorted the pins and it powered on! I was amazed. I carefully connected all the components one at a time and it was fully working again, even the power switch. I tried shutting down, restarting multiple times and left it off for several hours and it fired up no problem every time. I was not sure what happened, but was just glad it was working again.

The most bizarre thing happened a few days later when the 2 other PC’s in the same office (exact same spec) were doing EXACTLY the same thing. I did the same thing, stripped them down and they would not power up at all even when shorting out the pins. I left them overnight again last night and guess what? Today they both powered on, no problem.

Please can someone explain this as I have NEVER come across anything like this before. We have 9 more of these PC's in other departments and they are working just fine. I thought there could be a power spike issue in the office, but I was working on these pc's in my own office in another building. Here are the specs:

CPU - AMD Ryzen 5 3600X
Motherboard - ASUS PRIME B450-PLUS
Memory - 8GB Corsair VENGEANCE DDR4 2666MHz (2 x 4GB)
Graphics Card - 1GB NVIDIA GEFORCE 710 - DVI, HDMI, VGA
SSD - 250GB Samsung 860 EVO 2.5"
Power Supply - CORSAIR VS-350

Just for yuks.....measure the input power in your office vs the other office.

 

[Solan Goose]

Just for yuks.....measure the input power in your office vs the other office.

Thanks for your reply. I was thinking that it could somehow be a power issue in the office, but they seem to run fine unless they are shutdown overnight. When I tried to power up the pc's in a different building, still nothing. It's so bizarre that leaving them overnight enables them to power on again the next day is if nothing has happened. There must be a common explanation, as it's happening to 3 identical pc's. We have booked an electrician to test the power in the office, but I cannot see why it would cause this. I would expect a surge to kill the board or components.

 

[Grobe]

all have worked flawlessly for 3 years until recently. I have had issues with 3 of these PC's which are all in the same office. It started off with one of the PC's initially and now all 3 have the exact same issue.

Ok, since I've alredy read the rest of your post knowing more pc's are affected, this strongly indicates that there are a failure in this particular model. From what you describe, some possible culprits may be

• Manufacturer have used very bad capacitors. Intermittent failure at first can support this claim.
• Other weakness in components, but this is more rare than capacitors. Power transistors (especially those used in smtp voltage regulators) doesn't tend to "wake up" like this and is not likely the culprit (i.e. still points to capacitors).
• Some electrical failure due to bad choice of materials (e.g. manufacturer have put Cu directly in contact with Al that will cause corrosion over time).
• Additional info: For capacitors and possible bad choice of materials, the pace of the degrading process may variate slightly dependent of environmental factors such as humidity and temperature - this may explain why one office is affected earlier.

But
And also (this heavily depend on your location and the local power company and/or building electric conditions) let's not forget possible culprits outside. Consider if you have a building with poor electrical wiring, or the local power company have issues with voltage stability (more prone to voltage spikes).

Contrary to what many believe, a voltage spike is fully capable to traverse through smps circuit - ie a normal power supply - and thus cause damage to main board of computer. In this case - The office first affected may be electrically closer to the nearest circuit service panel (shh.. Google Translate is adamant this term should be "safety cabinet" in English, thanks for nothing Google). If this is the case and the other offices are placed on the same branch circuit, then it make sense that this computers goes first because the input circuit on the PCU will have some dampening effect on voltage spikes and thus serve as sort of a very poor over voltage protection, very poor but just enough so that the computers further down the same branch circuit is able to live longer.

but no fan movement at all from PSU, CPU or MB.

Do you expect the fan on the PSU to start immediately after power on ?

 

[Solan Goose]

Ok, since I've alredy read the rest of your post knowing more pc's are affected, this strongly indicates that there are a failure in this particular model. From what you describe, some possible culprits may be

• Manufacturer have used very bad capacitors. Intermittent failure at first can support this claim.
• Other weakness in components, but this is more rare than capacitors. Power transistors (especially those used in smtp voltage regulators) doesn't tend to "wake up" like this and is not likely the culprit (i.e. still points to capacitors).
• Some electrical failure due to bad choice of materials (e.g. manufacturer have put Cu directly in contact with Al that will cause corrosion over time).
• Additional info: For capacitors and possible bad choice of materials, the pace of the degrading process may variate slightly dependent of environmental factors such as humidity and temperature - this may explain why one office is affected earlier.

But
And also (this heavily depend on your location and the local power company and/or building electric conditions) let's not forget possible culprits outside. Consider if you have a building with poor electrical wiring, or the local power company have issues with voltage stability (more prone to voltage spikes).

Contrary to what many believe, a voltage spike is fully capable to traverse through smps circuit - ie a normal power supply - and thus cause damage to main board of computer. In this case - The office first affected may be electrically closer to the nearest circuit service panel (shh.. Google Translate is adamant this term should be "safety cabinet" in English, thanks for nothing Google). If this is the case and the other offices are placed on the same branch circuit, then it make sense that this computers goes first because the input circuit on the PCU will have some dampening effect on voltage spikes and thus serve as sort of a very poor over voltage protection, very poor but just enough so that the computers further down the same branch circuit is able to live longer.





Do you expect the fan on the PSU to start immediately after power on ?

Thanks for your detailed reply. The thing that baffles me is that the mainboards or components are not being damaged because they eventually work after leaving them untouched overnight or longer. It's almost as if the CPU or motherboard (nothing else was connected, PSU swapped) goes into a lockdown state after a power on the next morning after being shutdown overnight. I don't expect the PSU fan to come on from initial power up, but the chassis and CPU fans certainly. The build components are pretty mainstream and are not what I would class as bottom of the pile or poor quality. It's a very simple office pc build with stock air cooler for the CPU and no memory overclocks for cpu or ram. I chose these over a standard Dell unit as there were better upgrade options and the components were (on paper) better. I am very open for it to be a particular issue with the hardware, but I cannot think of anything else except the motherboard and CPU that would be the issue. 9 other pc's of the same build and age are still running in other offices with no issues.

 

[Eximo]

Have you tried new CMOS batteries?

Flaky behavior solved with long zero power states can be a sign of a battery with a low voltage.

Also the behavior of PSU OCP and OVP circuits. They can take some time to reset back to normal after a power spike.

Stray PoE? Voltage induction into ethernet, ground issues between two locations? I've measured 50V AC pumping through a parallel cable that had to go about 50 ft. Solution was to sink a new ground rod near the equipment (computer was in another room for dust reasons)

 

[Solan Goose]

Have you tried new CMOS batteries?

Flaky behavior solved with long zero power states can be a sign of a battery with a low voltage.

Also the behavior of PSU OCP and OVP circuits. They can take some time to reset back to normal after a power spike.

Stray PoE? Voltage induction into ethernet, ground issues between two locations? I've measured 50V AC pumping through a parallel cable that had to go about 50 ft. Solution was to sink a new ground rod near the equipment (computer was in another room for dust reasons)

I did try removing the CMOS battery for several minutes on one of them, but it made no difference. I did not think a low powered/dead CMOS battery would prevent POST. I will try new batteries though. The other things you mentioned in your post are way over my head. I was interested in your 'stray PoE' comment. Not sure what that means, but I can say that since these PC's were moved into this office, they are now connected to a PoE switch (non PoE previously) as there are PoE phones in this office too. It's actually a 48 port CISCO Catalyst PoE switch. I am not aware of any other devices connected to this switch that have issues. There are other offices too that have this same model of PoE switch with the exact same computers connected and have not had issues.

I still cannot understand how a pc can be stripped down to nothing but a PSU, motherboard and CPU and not even try to post (only mainboard LED's illuminated) by shorting the power on pins on the motherboard system panel connector (not the 24 pin ATX motherboard connecter) and yet, left overnight will magically power up when the pins are shorted or connected to a power switch. As I said before, I even swapped out the PSU with a fully working one off the shelf and still no post. It's as if the motherboard (or CPU?) goes into some kind of power on prevention hibernation.

Surely someone has come across this before.

 

[Eximo]

Improperly wired ethernet cables plus PoE can lead to voltages going where they shouldn't. Just something to keep in mind.

You do need memory to POST, the CPU can't run on its own. POST does include analog electronic steps, if there is a fault in any of the power circuits it can prevent a latching circuit from holding. So yes, a faulty or leaky component could be causing low voltage where it shouldn't be, causing a failure to POST. If multiple units of the same manufacture date show the same problem, it is likely a common fault amongst them.

I've encountered many no POST situations, the solution to all of them has been different. Mouse urine on a modem one time, for example.